1. Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, 2, Jhuoyue Road, Nanzih, Kaohsiung City 811, Taiwan, R.O.C., Department of Occupational Safety and Health, China Medical University, 91 Hsueh-Shih Road, Taichung 40402, Taiwan, R.O.C., and Department of Environmental and Safety Engineering, National Yunlin University of Science and Technology, 123, University Road, Sec. 3, Yunlin 64002, Taiwan, R.O.C.